OF THE American Philosophical Society HELD AT PHILADELPHIA FOR PROMOTING USEFUL KNOWLEDGE VOLUME XLVI JANUARY TO DECEMBER 1907 PHILADELPHIA THE AMERICAN PHILOSOPHICAL SOCIETY 1907 The Geology of the San Francisco Peninsula. By RODERIC Crandall, The Cathodic Precipitation of Carbon. By WILLIAM BLUM and EDGAR 65 65 BERTON........ The Effect of Imperceptible Shadows on the Judgment of Distance. EDWARD BRADFORD TITCHENER and WILLIAM HENRY PYLE................... Note as to the Measurement of the Action of Water upon Metals. By The Progress of the Isthmian Canal. The Association Theory of Solutions. By WILLIAM FRANCIS MAGIE... 138 The Groups which are Generated by two Operators of Orders Two and Four Respectively whose Commutator is of Order Two. By G. A. |